1. Field of the Invention
The present invention relates generally to drag bits and more particularly to drag bits utilizing cutters made of synthetic diamond material.
2. Description of the Prior Art
Conventional drag bits usually comprise a steel bit body having an upper end adapted to be attached to the bottom of a drill string. The lower end of the bit body comprises the cutting face which includes a plurality of cutting elements mounted thereon. The cutting elements may consist of a quantity of diamonds bonded to the face of the bit body.
Recently cutting elements utilizing synthetic diamonds have also been used. Each of these cutting elements comprises a slug preferably made of tungsten carbide which is substantially cylindrical in shape with the exception that one side thereof is planar in order to receive a disc of synthetic diamond material which is bonded thereto. The cylindrical base of the slug is adapted to be press fitted into bores formed in the face of the steel bit body. Each slug is positioned in its bore to have the face of the synthetic diamond disc oriented along the radius of the bit body facing the direction of rotation. The cutting edges of the synthetic diamond discs are then able to gouge away the earth formation at the bore hole bottom as the bit body is rotated on the bottom.
A major problem with such drag bits is that the slugs do not remain fixed within the bit body. During the cutting operations, these slugs often rotate within their bores which cause the cutting edges of the elements to face away from the direction of travel. When this occurs, the tungsten carbide slugs become worn and often become dislodged from the bores. This, of course, is deleterious to the cutting operation of the drag bit.
Another problem with conventional drag bits of the type described above is that, during operation, the face of the steel bit body becomes worn due to contact with the bore hole bottom and the cuttings located at the bottom of the bore hole. As a result, this wearing action causes the support around the base of the tungsten carbide slugs to erode which, in turn, causes the slugs to become dislodged.